[3.2.x] Fixed header underlines in performance docs.
[3.2.x] Fixed header underlines in performance docs.

Backport of ecf8af79355c8daa67722bd0de946b351f7f613d from main

koordinates/django,koordinates/django,wkschwartz/django,wkschwartz/django,wkschwartz/django,koordinates/django,koordinates/django,wkschwartz/django